NILFS_CHECKPOINT_FNS(SNAPSHOT, snapshot)
NILFS_CHECKPOINT_FNS(INVALID, invalid)
-NILFS_CHECKPOINT_FNS(SKETCH, sketch)
/**
* struct nilfs_cpinfo - checkpoint information
NILFS_CPINFO_FNS(SNAPSHOT, snapshot)
NILFS_CPINFO_FNS(INVALID, invalid)
-NILFS_CPINFO_FNS(SKETCH, sketch)
/**